Existing lens ferrule designs that use single-mode optical fibers create significant return loss, also known as back-reflection. Within a current lensed ferrule, light exits the fiber and if there is a gap between the fiber and ferrule, the light travels through an optically transparent adhesive, followed by several hundreds of microns of the optical polymer used to make the ferrules, and then exits the polymer ferrule material, typically through a lens. The refractive index of the polymer ferrule material differs significantly from the fiber, which causes the primary reflection of light as the light transmits through the index of refraction change of the ferrule from the optically transparent adhesive. The light reflecting back into the optical fiber contributes to a return loss.
In order to reduce the reflection of the light back in to the optical fiber and the ferrule itself, Applicant has determined that if the surface of the ferrule where the light enters after leaving the optical fiber and adhesive is disposed at an angle, the reflection can be reduced to an acceptable amount. The reflection may also be reduced if the front end of the optical fiber is disposed some distance from the entrance surface.